Especially in underpressurized air conditioning systems the ventilation is based on underpressurizing, my means of which air is sucked in. Unless there are controlled pathways for replacement air, air tends to drift inside a building through all possible routes. In order to control the replacement air flows, there are in practice first of all passive that is without a blower naturally operating replacement air valves that have typically both mechanical adjustment arrangements for adjusting the amount of replacement air and filter arrangements in order to filter replacement air being fed indoors and to dampen the noise coming from outside. On the other hand, there are in practice also active that is blower operated replacement air valves and furthermore also replacement air valves provided with heating arrangements, with which the production of replacement air may be adjusted e.g. with adjustment mechanisms or by adjusting the speed of rotation of the blower.
One problem in producing replacement air is the movement of the cold outdoor air, being fed indoors, which causes a so called feeling of draft. The optimal functioning of an air replacement valve is based on a flow of warm indoor air passing upwards, which lifts the cold replacement air to go upwards along the inner surface of the ceiling. When such a flow slows down it gets thus warmer by getting mixed with the warm air close to the ceiling, causing thus not any feeling of draft to be noticed in the living space of the apartment. This is why the replacement air valves are usually installed above radiators.
Nowadays energy efficiency of buildings has been improved and radiators have been exchanged e.g. into low-heat radiators or the heating has been switched to underfloor heating, due to which the air flow passing upwards along the walls has diminished and is thus not able to eliminate the feeling of draft on its own. On the other hand, in traditional construction technique the flow of replacement air often takes place in a decentralized manner e.g. through window gaps, whereby the speed of replacement air flow is relatively slow. In these types of cases, e.g. in connection with window renovation according to today's practice, windows have either been tightened and the apartments have been provided with separate replacement air valves or the original windows have been replaced with new windows having replacement air valves, after which the flow of replacement air into the apartment takes place at a higher speed in a spotlike manner. Actually the speed of replacement air flow rises even more, because in traditional renovation usually all windows are tightened and only some are provided with replacement air valves. Due to the feeling of draft, the replacement air valves are often closed during a heating season, which disrupts the ventilation. However, from the point of view of the functioning of the ventilation, it is important that feeding of replacement air occurs as planned regardless of outside temperature.
Furthermore, especially when placing the window valves in spaces that have e.g. curtain boxes, the natural flow of replacement air is blocked, which is why it may flow down e.g. along the window surface causing both a feeling of draft and the moistening/frosting of the inner surface of the window, which also often leads to the closure of the replacement air valves. E.g. in an apartment building, when one or more residents close their replacement air valves and the constant-speed exhaust air volume does not diminish, a higher under-pressure is caused in other apartments and thus also a stronger feeling of draft, which brings about a need for other residents to also close the replacement air valves.
Preventing the free and controlled feed flow of replacement air causes a distortion for the pathways of replacement air in the buildings, in which case air enters through structures, hallways and even through the sewer system. This causes unclean indoor air and strains the structures. Symptoms of these types of problems are e.g. smells in the apartments that are drifted from e.g. neighbours, the hallway, the sewer etc. and sewer clogs. Thus, e.g. in ground floor buildings, such as in terraced houses or single-family houses and in the lower floors in apartment buildings, but the same way also in higher floors through e.g. elevator shafts and other vertical shafts, the closure of the replacement air valves causes the replacement air to pass through the ground and the structures. In this case, e.g. natural gases, such as e.g. radon, are basically being sucked into the apartment, which as such is a significant health risk, controlling of which requires measuring actions and based on which, when the threshold values are exceeded, renovating actions, such as assembling a radon well etc.
Especially in order to control the feeding of outdoor air to be fed into a building's indoor space, a supply air apparatus is previously known from e.g. patent publication GB 2260807, which supply air apparatus comprises a flow space with flow connections in connection with an outdoor air flow way in between an indoor space of a building and outdoor air in order to mix outdoor air and indoor air with each other, a blower arrangement, such as a blower functioning on axial principle, and a blow flow arrangement in order to lead the mixed air inside the building.
With a solution described above it is possible to carry out the feeding of outdoor air into an indoor space by mixing indoor air, being produced from an apartment by an indoor air suction blower, with outdoor air, being fed into a suction channel by a blower, by feeding the mixed air to pass near the ceiling of the room guided by a lower guide. In this solution, the volume flow of the mixed air flow being blown into the apartment is to be regulated by adjusting the functioning of the blower, whereby the air being blown into the room is also, if needed, heated by auxiliary heaters existing near the ceiling. In addition, the air blower that circulates the indoor air is being guided according to outdoor air temperature in a way that its capacity is highest when outdoor air temperature is low and lowest when outdoor air temperature is high.
A disadvantage of the above mentioned solution is the large amount of apparatuses that is the blowers for both outside and inside air used therein, in addition to which the principle according to the solution may not be used as such in connection with existing replacement air valves that usually have already at least a mechanical adjustment arrangement in order to adjust the amount of outdoor air to be brought through the replacement air valve into the apartment.